Generally a lav in the "hot zone" either on the groom or the officiant will primarily pick up the officiant, and the all important vows. better yet, a mic on each, for redundancy. While it is possible to get white lavs, generally you wouldn't mic the bride - you may need to boost her in post vs. the groom, but you should get pretty usable signal.

If the buzz was as loud as you say, it might have created a "noise floor" high enough to cause problems, but generally the idea behind the lav is to pick up stuff in close proximity, not "house" or ambient noises - thus why it's the preferred method, whether feeding a small digital recorder or a wireless (both have their proponents here, I have BOTH a customized bluetooth mic with lav added for the Sony handycams up front, AND iRivers with GS mics, plus a couple more bluetooths that can be hung in close proximity without being obtrusive. I believe in triple redundancy if at all possible, because nothing ever goes wrong, as you're finding out <wink>!

I have one lav on the groom and it's easy to pick up sound in his near proximity. Check out this video

However, that doesn't work at Catholic weddings. Now I also have a different method to place another audio recorder near the DJ speaker

Hey Taky, what kind of mics are you using on your olympus? I have olympus with giant squid pavs and they're awful, every time the groom starts speaking it peaks really high and distorts its rare that I get anything good from the DVR.

I thought it was because of the AGC but I bet its just my lavs are too poorly made.

I'm using an Olympus Michael. Check out the link here.

Wireless Mics vs Voice Recorders | L.A. Color Blog

I do have to switch the Michael sensitivity to low to avoid distortion.

I often try to position one of my camera near the speaker.. that way, whatever the audience is hearing, I'll be recording it. In one instance, I even put my RODE on a light stand, place it near a speaker, and pull an extension cable to my camera. Works well.

I've actually tried planting a digital recorder with the lav sticking to the speaker stand (around 2 m below the speaker) and the audio actually turned out well. The stand must've carried the audio through and the lav was able to pick it up.

Don't rely on the mixer/DJ as they could do things that unknown by you might ruin the quality of the audio.

Just make sure you're place an 'omni-directional' mic on the groom and not a 'directional' mic. The directional style mic will pick up mostly the groom while an omni-directional will better cover the bride as well.